There is a sheet post-processing apparatus that applies post-processing such as sorting and stapling to a plurality of sheets conveyed from an image forming apparatus. The sheet post-processing apparatus includes a plurality of conveying paths for applying different kinds of post-processing to the sheets and a discharge unit in which an opening section for discharging the sheets to the outside is formed. However, if the opening section provided in common to the plurality of conveying paths is increased in size, it is likely that noise such as operation sound leaking to the outside increases.